Unfortunately,​ there is no definitive way to determine the number of factors. You probably try to do multiple ways explained here, and see how many factors each of them is suggesting. They should suggest you more or less the same number of factors, so you can have a pretty good idea of how many factors you should choose. ​

Unfortunately,​ there is no definitive way to determine the number of factors. You probably try to do multiple ways explained here, and see how many factors each of them is suggesting. They should suggest you more or less the same number of factors, so you can have a pretty good idea of how many factors you should choose. ​